1. Field of the Invention
The present invention relates to a technique of printing using a spot color printing material.
2. Description of the Related Art
There has recently been a growth in color laser printers using so-called “spot color printing materials” in addition to normal color toners such as CMYK (cyan, magenta, yellow, and black). The spot color printing materials include color toners of having colors such as red, blue, and white other than CMYK and also colorless toners such as a transparent toner (to be referred to as a “clear toner” hereinafter) to be used to add a transparent image to a printed product.
The user can generate a high-value-added printed product by selectively using various kinds of spot color printing materials in accordance with the application purpose. For example, a printing apparatus using a clear toner can apply clear toner printing to the entire surface or part of a paper sheet as well as color printing using the CMYK color toners, thereby attaining a glossy or shining appearance like a photo (Japanese Patent Laid-Open No. 2006-309685).
To execute printing using the clear toner, an image processing apparatus incorporates a mechanism for transferring the clear toner and the CMYK toners that are colored toners to a paper sheet and then fixing the colored toner images and the clear toner image to the paper sheet by one fixing. An output product using the clear toner is thus created.
However, addition of the arrangement for printing using the clear toner poses problems. For example, a problem concerning the applied toner amount arises. More specifically, an image processing apparatus has a limit (applied amount limit) to the toner amount fixable by one fixing per unit area of the printing target paper. Hence, to suppress the toner amount within the applied amount limit, the clear toner cannot sufficiently be used in a region where the CMYK toners are used in large amounts.
An image processing system has been proposed, which is constructed by connecting an image processing apparatus for printing using colored toners and an image processing apparatus for printing using a clear toner so as to create an output product using the clear toner (Japanese Patent Laid-Open No. 2008-145595). For example, there is provided, for a user who uses a clear toner, an image processing system formed by connecting an image processing apparatus (apparatus of the preceding stage) for performing transfer/fixing and printing using colored toners and an image processing apparatus (apparatus of the succeeding stage) for performing transfer/fixing and printing using a clear toner. This arrangement allows to sufficiently use both the CMYK toners and the clear toner for a print target object.
However, it is difficult to flexibly switch the clear toner usage method for each page.
For example, in Japanese Patent Laid-Open No. 2006-309685, to perform printing using the clear toner, the user designates the range to be printed using the clear toner on the user interface of the printer driver. If the user wants to change the designated range on the page basis in a multiple page job, the range designation needs to be done in each page. Then, only the image data of the designated portion is printed using the clear toner. Printing using the clear toner may be designated using an α plane or the like. Note that the description in the following embodiments will be done assuming an application supporting clear data addition.
At this time, for example, if the user wants to print not to check the printing effect of the clear toner but to check the page composition, the settings are changed not to use the clear toner in a full clear page so as to suppress waste of toners. In the conventional method, however, if the range designation has been done for full clear printing, the clear toner printing designation needs to be canceled for the check printing. If the system allows to specifically designate the clear toner printing range in all pages, the operation of canceling the clear toner printing designation is very cumbersome for the user. In addition, since the settings for the page composition check printing need to be different from the settings for actual printing using the clear toner, the risk to cause an error is high.
Furthermore, when the clear toner is partially applied to an image, the range designation is often done to overcoat an object.
For example, examine a case in which the clear toner is applied to a black line object. In this case, without much concern for printing, the document data creator designs the data of the portion to be printed using the clear toner in the same line width as that of a black line of the background of the region to be printed using the clear toner. However, when the black line is reproduced using the four CMYK toners, misregistration may occur between the colors, and the line may be reproduced thicker than that reproduced using only the K toner. This causes misregistration between the clear toner itself and other colors. That is, to implement overcoat by the clear toner, the lines need to be printed thicker than the black line object in the background range.
The above-described contents also apply to an image object and a graphic. To overcoat an image object or a graphic with the clear toner, the document data creator designs the clear data in the same size as that of the image object or the graphic.
However, since the misregistration occurs between the CMYK toners and the clear toner, the portion where the CMYK toners are printed cannot be overcoated with the clear toner in the same size.
Especially, in the printing system including the printing apparatuses connected to each other, the first printing apparatus of the preceding stage performs printing using the color toners, and the second printing apparatus of the succeeding stage then performs printing using the clear toner. That is, since an image is printed on one paper sheet using the plurality of apparatuses, the registration errors may occur in printing at a higher possibility. In reduction printing or reduction layout printing as well, the misregistration amount feels large because of the small object size, although the misregistration amount is the same as in normal size printing.